I'm 19, soon to be 20 and live in a high priced gated community. I go to college which is located a mere 12 miles from my house and come home everyday rather than stay in a dorm only because my room is like living in luxury. My parents are seldom home on weekends and do work long hours during the week and I pretty much have the run of the house. Next door to my house lives Mallory who is 23 not in school and doesn't work and even though I have known her for a few years we were never friends until this past spring. Her parents are also away often and she began inviting me for lunch and calling me a lot just to talk. Mallory is not at all cute and is a big girl both in height and weight. She was fun to talk to so whenever she called and asked me to come over her house I did mainly because they have an in the ground pool. We began going in the pool and although she is very big she isn't really fat just a big girl. She knows I have a girlfriend and began asking me personal questions about my relationship. Its wasn't to bad at first but then she began asking me if I had sex and if my girlfriend gave me oral and even began asking me if I was circumcised and how big my penis was. I thought it strange but to be honest just the way she asked the questions I sometimes got an erection. Right at the end of May she noticed I had a hard on when I was still in my bathing suit and right away told me she sees it. I felt awkward but she made it worse when she kept trying to get me to show her my penis. We were just standing there talking and for some reason the more she talked about showing her my penis the more my erection wouldn't go down. Without any warning at all Mallory just reached out and pulled my swimming trunks down to my ankles. As I bent over to pull them up she pushed me down on a lounge chair and took them off me. I did cover my penis and scrotum with my hands but I still had an erection and instead of being real embarrassed about it i joined her laughing about it. She said be right back and within a minute tossed me a tube of body lotion and asked me to jerk off for her and said please about 20 times. I never did this before and not even in front of my girlfriend but I put some of the lotion on my hand and let Mallory watch me masturbate. She never takes off her bathing suit but eveeytime I go to her pool since then I end up masturbating for her. She only tells me she likes to see me cum and admitted to me she is still a virgin and never saw an adult guys penis unless it was porn. As much as it was unlike me to expose myself in front of her and even more unlike me to masturbate with her watching I was never really embarrassed about it. I swim at her house twice a week and let her watch me masturbate every time I'm there.